<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            display: flex;
            width: 100%;
            height: 600px;
        }

        .toggle{
            height: 100vh;
            width: 200px;
            border: 1px solid #000;
        }

        .toggle a {
            display: block;
        }

        iframe {
            width: 100vw;
            height: 100vh;
            border: 1px solid #ccc;
        }
    </style>
</head>

<body>

    <!--    1-需要给标签 设置 href 以及 target  属性
    2- iframe 设置 name属性
    3- a标签的target = iframe name属性 -->
    <div class="menu">
        <a target="toggle" href="https://www.163.com/">网易</a>
        <br>
        <a target="toggle" href="03-被套的页面.html">03-被套的页面</a>
    </div>

    <iframe src="" frameborder="0" name="toggle"></iframe>
</body>

</html>